Can aroma therapy and essential oils be used past the expiration date?

Yes. Expiration dates on medicines, vitamins and herbs are often unreliable; while some drugs may go bad after a certain period, an essential oil is likely to remain beneficial for quite awhile after the expiration date. There is a chance it may become somewhat less potent over time but it is unlikely to be harmful in any way, especially if it is a pure essential oil. If it still smells good try it!